Lily Munster is the matriarch of the Munster family. She is very close with her niece, Marilyn. She has a werewolf for a brother, who appears in one episode, and a sister who is mentioned a few times who is Marilyn's mother. Lily is the voice of reason in the Munster household, often relied upon to set problems right, and typically mediates when Herman and Grandpa squabble.

Lily also has a fiery temper. While she is deeply in love with Herman ("Pussycat," as she calls him), she also frequently gets very angry at him (due to his frequent stupidity and occasional selfishness), and Herman often meekly discloses his fear (to others) of being on the receiving end of her wrath. She also has reprimanded her own father (Grandpa) on several occasions for his own foolish actions and stubborn self-righteousness.